This invention relates to a display control device which controls display of input video signals, and particularly to a display control device which controls display according to various types of display formats.
In recent years, as a display system for various types of demonstration in a studio or a theater, a multivision system is well known. The multivision system is a large size display system which allows various types of display patterns such as displaying a large size video image on a large screen formed by combining a plurality of display units, each based on a projection TV system, in both vertical and horizontal directions, as providing a screen comprising multiple blocks each having multiple display units to display several different video images on the screen, or as displaying different video images on each display unit.
Development of various types of display patterns on the display system as described above is controlled by a display control device called a multi-video processor. The display patterns are largely classified to a single screen on which the same video image is displayed by each display unit, and an enlarged screen on which a large video image is displayed by using particular ones or all of the display units.
Thus, in controlling display of an enlarged video image, as the video image is enlarged in both vertical and lateral directions by the same magnification, a ratio of vertical length vs lateral length is kept at a constant level, so that the enlarged video image is a similar figure to the original video image. Also, as video signals are input to a display pattern control device through one channel, a similar display pattern is provided. Thus, with the conventional technology, it is difficult to display different modes of video images (based on different combination of positions and size) in various patterns. Also, if a frame of a video image is adjusted in a particular display unit by an arbitrary magnification, other frames not requiring adjustment are also changed, and continuity of video images over multiple display units adjacent to each other is lost, thus displacement of display being generated in each display unit.
Furthermore, also in a display system comprising a single display unit, when it is necessary to display a video image in an enlarged form, display control is performed by interpolating input video signals to increase the density of picture elements. This display control by means of interpolation is based on an interlace scanning system wherein even number fields are scanned after scanning odd number fields, and interpolation scan signals are generated at scanning line positions in even number fields depending on scan signals in odd number fields when scanning the odd number fields. Thus, the picture quality is kept at a constant level by raising the density of picture elements by means of interpolation.
In the display control by means of interpolation, however, linear interpolation is made at a particular ratio prescribed beforehand to raise the density of picture elements. If this method is applied to enlarge a video image in vertical and horizontal directions at an optional magnification, respectively, also the interporaltion ratio becomes identical, and sometimes the density of picture elements in the enlarged display may be insufficient, excluding the special cases where the number of points for interpolation is suited to the magnification or the number of increased scanning lines is suited to the magnification especially in case of enlargement in the vertical direction, good resolution can not be obtained. Also, if the conventional technology is applied to a multivision system having multiple display units wherein a video image is provided in each of the display units at a different magnification, respectively, the density of picture elements varies from display unit to display unit, so that display at a homogeneous display can not be performed.